New olfactory research suggests
that when it comes to tracking
scent at ground-level on open
terrain, the average human's
sense of smell is stronger
than most people believe.

"There's this general assumption
that people have a bad sense
of smell," said study lead
author Jess Porter, a Ph.D.
candidate in biophysics at
the University of California
at Berkeley. "But we found
that people can certainly
sniff their way accurately
around a spatial context --
although less successfully
and slower if they have only
one nostril to work with."

The new American-Israeli
study, published online Dec.
17 in Nature Neuroscience,
reports that people can, in
fact, be trained to rely exclusively
on ground-level smelling to
successfully navigate unknown
territory. In fact, they instinctively
mimic certain animal behaviors,
including enlisting each nostril
to independently identify
distinct smells and "triangulate"
a path.

Porter joined Berkeley psychology
professor Noam Sobel and a
team of colleagues. Together,
they conducted five experiments
aimed at assessing people's
ability to track scents.

Enlisting anywhere from four
to 32 male and female participants
for the various tests, the
researchers worked in an open
field.

The subjects were first blindfolded
and ear-plugged before being
asked to follow a 10-meter
trail scented with "chocolate
essential oil." They followed
the trial by moving close
to the ground on their hands
and knees and wearing thick
gloves, with only their noses
to guide them.

Two-thirds of the participants
were able to do so. However,
when their noses were plugged
to cut off the ability to
smell, none of them could
follow the path.

To test if "practice makes
perfect," two men and two
women were subsequently trained
to complete the same task
three times a day for three
days, stretched over a two-week
period.

Porter and her team found
that this type of training
allowed subjects to track
scent trails faster and with
greater accuracy. In fact,
their speed of execution doubled
within a few days. The researchers
believe more training might
boost efficiency even higher.

Porter's group also found
that as the speed of trained
scent tracking increased,
so did sniffing frequency.
In this regard, they noted
that dogs sniff much faster
than humans, perhaps accounting
for their superior tracking
abilities.

A third experiment revealed
that each of a person's two
nostrils inhales distinct
smells, pulled from non-overlapping
regions in the air. The researchers
pointed out that prior studies
have shown that scent "plumes"
in the open are often confined
to such small areas that only
one nostril will pick it up,
while the other will not.

The fourth test followed
up on this finding by asking
14 subjects to complete the
field-tracking experiment,
but with one nostril taped
shut.

Single-nostril tracking was
much less accurate (36 percent
versus 66 percent) and 26
percent slower compared to
using both nostrils.

Finally, the authors conducted
a final test using a special
mask that allowed both nostrils
to inhale, but forced incoming
air to join together into
a single air stream inside
the middle of the nose.

Porter and her associates
found that this "unified nostril"
method was 24 percent slower
and much less accurate than
tracking completed normally.

This shows that optimal human
tracking requires the individual
use of each nostril to better
distinguish smells as people
home in on an appropriate
route.

The team concluded that,
just as happens with animals,
people's capacity to smell
can be harnessed to great
effect.

Still, for most people,
eyes remain the key window
on the world.

"I think it's fair to say
that humans are very, very
visual, whereas an animal
that lives in the dark is
primarily olfactory," noted
Porter. "And people do have
this idea that as our sense
of vision and hearing has
become so prominent, we've
lost some of our olfactory
capability."

That might not be the full
story, however. "We think
it's maybe that we don't place
an emphasis on our sense of
smell," Porter suggested.
"Because the underlying mechanisms
are still there -- to a greater
extent than we maybe notice
them. And if we place demands
on them and train ourselves,
our ability to follow a spatial
path can improve a lot."

George Preti, a member of
Monell Chemical Senses Center
in Philadelphia, a research
institute devoted the science
of taste and smell, agreed
that humans' olfactory talents
can be honed with practice.

"Our sense of smell may
not be as good as dogs or
rodents, but it's still pretty
acute when we use it correctly,"
he said. "I'm an expert in
the chemistry of human odors,
and I can tell you that folks
that use it for a living,
like perfumers, do improve
their use of it and make themselves
more consciously sensitive
to that kind of input."

"Smell is important in our
everyday life," Preti added.
"And we use it a lot. Not
just for evaluating food,
but also for how we're perceived
by the rest of the world.
So, I'd say that humans certainly
do have very sensitive noses
-- regardless of what people
might think."